Some claim the number is drawn from the California criminal codes used to punish the use or distribution of marijuana. But the state’s 420 code actually applies to obstructing entry on public land. So, not quite.

But the rumor sounds a lot like …

The legend of the police radio code

Neither LAPD nor NYPD even have a code 420. San Francisco Police have one, but it’s for a “juvenile disturbance.”

Seems a bit of a stretch. And Dylan himself has never confirmed any link.

The story that appears to hold the most water is …

The legend of the Waldos

According to Chris Conrad, curator of the Oaksterdam Cannabis Museum in Oakland, California, 420 started as a secret code among high schoolers in the early 1970s.

A group of friends at San Rafael High School in Marin County, California, who called themselves “the Waldos,” would often meet at 4:20 p.m. to get high.

For them, it was an ideal time: They were out of school but their parents still weren’t home, giving them a window of unsupervised freedom. They met at that time every day near a statue of Louis Pasteur, the scientist who pioneered pasteurization.

The 4:20 time became a code for them to use in front of their unsuspecting parents, and 420 gradually spread from there — possibly via Grateful Dead followers — across California and beyond. It’s even the number of a California Senate bill that established the state’s medial marijuana program.

What was shorthand for a group of friends can now be seen on T-shirts, in Tinder bios (420 friendly) and throughout pop culture.